This invention relates to a drywall trim piece for installing at an external right angle corner at which two drywall boards meet and which is provided with a bullnose corner bead.
In standard wall board construction practice, an external corner joint, formed where wall board of a first wall surface meets wall board of a second wall surface, may be covered with a protective corner bead. The corner bead is typically made of steel, formed as a single strip held in place against the wall boards of the two wall surfaces by nails or by a thin layer of joint compound between the flanges of the corner bead and the wall surfaces. When the corner bead has been secured in position, joint compound is applied over the flanges of the corner bead and the adjacent wall surfaces to provide a smooth finish.
After the drywall has been installed and finished, baseboard is typically installed along the base of each wall. At external corners, the two strips of baseboard material that meet at the corner are typically mitered to provide a uniform external surface profile up to the point at which the strips meet.
The conventional method of installing corner bead and baseboard is advantageous because it allows fairly wide tolerance on positioning the lower end of the corner bead. As long as the lower end of the corner bead is below the upper edge of the base board, there is no unsightly gap or rough edge. Since the base board is typically at least three inches wide, it is not necessary to cut the corner bead very accurately.
This technique for installation of drywall and baseboard has worked well when the corner bead has a substantially right angle profile because the exterior configuration of the corner bead, after the joint compound has been applied, matches the interior configuration of the baseboard at the corner. Recently, however, bullnose corner bead, in which the corner bead includes, between the planar flanges, an intermediate portion having a radius of curvature as large as one inch, has come into favor. If conventional 45xc2x0 miters are used in the baseboard material at an external corner provided with bullnose corner bead, there can be an unsightly gap between the exterior of the bullnose corner bead and the strips of baseboard material.
Several techniques have been developed for avoiding the problem created by the difference between the external configuration of the drywall corner and the internal configuration of the baseboard. One technique involves use of a trim piece which provides a transition between the curved exterior surface of the bullnose corner bead and the right angle internal corner of the baseboard. This trim piece is made of a hard synthetic polymer material. At its upper end, the trim piece has a tongue which is shaped and sized to fit under the bullnose corner bead. Just below the tongue, the exterior surface of the trim piece substantially matches the exterior surface of the corner bead. There is then a transition area, about xc2xd inch high, over which the configuration of the exterior surface changes from one that matches the exterior surface of the corner bead to a right angle, which matches the internal configuration of the baseboard corner. The corner bead is installed at the corner so that its lower end is slightly above the upper edge of the baseboard that is to be used. The trim piece is installed with its lower end resting on the floor and the tongue at its upper end is inserted under the lower end of the bullnose corner bead. The baseboard is then installed and the trim piece provides a smooth transition from the external configuration of the corner bead to the internal configuration of the baseboard corner.
In practice, the known trim piece is subject to several disadvantages. For example, the lower end of the corner bead must be accurately positioned to within about xc2xc inch above the upper edge of the baseboard material. Also, the height of the lower end of the corner bead determines the height of the baseboard and it is costly and inconvenient to use baseboard material of different height. Further, the height of the trim piece depends on the height of the baseboard material and therefore an installer who is working with several different heights of baseboard material must hold several different sizes of trim pieces in inventory, increasing the cost of inventory and giving rise to the danger that the wrong size pieces will be shipped to a particular job site.
In accordance with a first aspect of the invention there is provided a trim piece for installing at a drywall external right angle corner at which two drywall boards meet and which is provided with a bullnose corner bead having first and second flanges extending over the two drywall boards respectively and a convexly curved portion joining the first and second flanges, the first and second flanges having respective mutually parallel free edges, said trim piece comprising an intermediate portion which wraps over the convexly curved portion of the bullnose corner bead and has first and second edges extending parallel to the edges of the flanges of the corner bead and also has two opposite ends, first and second leaves attached to the intermediate portion of the trim piece at the first and second edges respectively, and first and second pins projecting from the first and second leaves respectively, the first and second pins being located so that when the trim piece is placed over the corner bead and the leaves are forced against the flanges of the corner bead, the pins are driven into the drywall boards and a flank of each pin bears firmly against a free edge of a flange of the corner bead, whereby the trim piece is held in position relative to the corner bead, and the intermediate portion of the trim piece including a transition region having a first end at one end of the intermediate portion and a second end spaced from the first end, the transition region having an interior surface at said first end matching closely the exterior surface of the corner bead at said first end and an exterior surface which is convexly curved at said first end and is right-angled at said second end and provides a transition from the convex curve to the right angle between said first and second ends.
In accordance with a second aspect of the invention there is provided a trim piece for installing at a drywall external right angle corner at which two drywall boards meet and which is provided with a bullnose corner bead having first and second flanges extending over the two drywall boards respectively and a convexly curved portion joining the first and second flanges, the first and second flanges having respective mutually parallel free edges, said trim piece comprising an intermediate portion which wraps over the convexly curved portion of the bullnose corner bead and has first and second edges extending parallel to the edges of the flanges of the corner bead and also has two opposite ends, and first and second leaves attached to the intermediate portion of the trim piece at the first and second edges respectively, and the intermediate portion of the trim piece including a transition region having a first end at one end of the intermediate portion and a second end spaced from the first end, the transition region having an interior surface at said first end matching closely the exterior surface of the corner bead at said first end and an exterior surface which is convexly curved at said first end and is right-angled at said second end and provides a transition from the convex curve to the right angle between said first and second ends.
In accordance with a third aspect of the invention there is provided a trim piece for installing at an intersection of three drywall external right angle corners each provided with a corner bead having first and second flanges, the flanges of each corner bead having respective substantially mutually parallel free edges that are substantially perpendicular to the free edges of the flanges of the other corner beads, said trim piece comprising a three-sided corner portion for fitting over the intersection, and three limbs that project from the corner portion for fitting over the three corner beads respectively, and wherein each limb includes two flanges that fit against respective flanges of the corner bead over which the limb extends.
In accordance with a fourth aspect of the invention there is provided a method of finishing an intersection of three drywall external right angle corners each provided with a corner bead having first and second flanges, the flanges of each corner bead having respective substantially mutually parallel free edges that are substantially perpendicular to the free edges of the flanges of the other corner beads, said method including providing a trim piece having a three-sided corner portion and three limbs that project from the corner portion, and wherein each limb includes two flanges that fit against respective flanges of the corner bead over which the limb extends, positioning the trim piece with the corner portion over the intersection of the drywall external corners and with the limbs over the corner beads respectively, and attaching the trim piece to the underlying structure.